Transmission of Feline Giardia
Giardia is contracted when a cat eats the giardia parasite in its cyst form. When the cyst reaches the cat's small intestine, it opens and releases a trophozoite. The trophoziote has flagella, which are hair-like structures that enable it to move. They attach themselves to the wall of the intestine and reproduce by division.
Vets aren't sure how many times the trophoziote divides, but they know that they eventually form new cysts that are passed in the feces.
There are several different species of giardia. Vets don't yet know if specific species infect specific hosts, or if infections are able to spread between species. There may be links between human giardia outbreaks and animals, both wild and domestic, infected with the parasite. For the time being, vets believe it's safest to assume that feline giardia is contagious to humans.
Symptoms and Diagnosis of Giardia Infection
Most giardia infections show no symptoms. When symptoms appear, they usually do so in younger cats.
The most common symptom is diarrhea. The stool may be pale in appearance, smell especially foul and look greasy. Cats suffering from giardia infection may lose weight, while their appetite remains the same. Giardia prevents absorption of nutrients, damages the lining of the intestine and interferes with the digestive process.
Feline giardia can be difficult to diagnose. The active protozoa are incredibly small, and they do not appear in each stool that is passed. Vets need to test stool samples every day for at least three days in order to find the giardia protozoa and make an accurate diagnosis.
Vets use a special procedure to find the active protozoa in the stool. They mix the stool with water and then examine it under high magnification. Because the active protozoa are moving, vets can see them under a microscope.
Giardia can often be found in firm stool in its cyst form, before active infection has occurred. Vets use a solution to separate the cysts from the stool, and then examine them under a microscope.
Treating and Preventing Feline Giardia
Treatment of giardia in cats is often a matter of debate. Cats may be asymptomatic carriers of the parasite for years, or throughout their entire lives. Since not much is known about giardia, most vets err on the side of caution and choose to treat even asymptomatic cats, to prevent transmission to humans.
Vets use a number of medications to treat both active and inactive giardia infection. These include:
- Fenbendazole
- Metronidazole
- Quinacrine hydrochloride
- Furazolidone
The parasite that causes giardia in cats can live outside the host's body for months. Lawns, parks, kennels, catteries and other areas contaminated with animal feces may also be contaminated with giardia. Avoid these areas if possible.
Treat infected animals, even when they are asymptomatic. Keep your home sanitary. Bleach, Lysol and ammonia all kill the giardia parasite.